414 VEGETABLE FORCING 
houses make beds 10 to 12 inches deep sometimes, but this 
is of doubtful expediency. The more generally approved 
plan is to use only the specially composted manure, mak- 
ing beds with a total depth of 8 to 10 inches, after the 
manure has been firmed or compressed by the use of a 
board or other convenient device. A certain amount of 
compacting of the manure is necessary to prevent it from 
becoming too loose and dry. 
After the beds have been filled, the temperature of the 
manure may rise for a few days and then it will begin to 
decline, but there should be no spawning until it is down 
to 75 degrees or preferably 70 degrees. The moisture of 
the beds between filling and spawning should also be 
carefully watched. If the manure has been properly pre- 
pared and the beds and houses are well constructed, 
there should be very little trouble in this connection. 
However, light sprinkling is sometimes necessary in 
order to maintain proper moisture conditions. A practi- 
cal test is to squeeze the compost in the hand at the time 
the beds are filled. If no drops of water are squeezed out 
and the hand remains distinctly moist, additional water 
is not required. But too much emphasis cannot be placed 
upon the importance of having perfect moisture condi- 
tions when the beds are filled. Skillful growers never 
water the manure in the beds. 
Spawn.—Success in growing mushrooms depends very 
largely upon the use of good spawn. English spawn was 
used almost exclusively in this country until a few years 
ago, and although it was regarded as the best, results 
from its use were very uncertain. Great credit is due 
Duggar for his work in developing pure culture spawns 
which have placed the whole proposition on a more cer- 
tain, scientific and satisfactory basis, thus making it com- 
parable to other lines of horticultural production. 
The making of pure culture spawn is in itself a special 
enterprise requiring skill and laboratory equipment, and 
